require 'builder'

module Rack
  class MusicIndex
    def initialize(app, options = {})
      @app = app

      init(options)
    end

    def init(options)
      @dirs = options
    end

    def call(env)
      status, headers, response = @app.call(env)

      path_info = env['PATH_INFO']

      update_files

      if dirs[path_info]
        headers['Content-Type'] = 'application/xml;charset=utf-8'
        body = podcast(env)
        headers["Content-Length"] = body.length.to_s
        response = [body]
        status = 200
      elsif static_paths.include?(path_info)
        body = open(static_paths[path_info], 'rb').read
        headers["Content-Type"] = 'audio/mpeg'
        headers["Content-Length"] = body.length.to_s
        response = [body]
        status = 200
      end

      [status, headers, response]
    end

    private

    def dirs
      @dirs
    end

    def files(media_dir)
      @files[media_dir]
    end

    def static_paths
      @static_paths
    end

    def update_files
      @files = {}
      @static_paths = {}

      dirs.each do |path, dir|
        @files[path] = Dir[dir + '/*.mp3']
        @files[path].each do |filename|
          @static_paths[path + '/' + ::File.basename(filename)] = filename
        end
      end
    end

    def podcast(env)
      path  = env['PATH_INFO']
      req   = Rack::Request.new(env)
      url   = req.url
      files = files(path)
      xml   = ::Builder::XmlMarkup.new

      xml.instruct! :xml, :version => '1.0'
      xml.rss :version => "2.0", 'xmlns:itunes' => 'http://www.itunes.com/dtds/podcast-1.0.dtd' do
        xml.channel do
          xml.title path
          xml.description 'Generated by Rack::MusicIndex'
          xml.link url

          files.each do |file|
            name = ::File.basename(file)
            item_link = url + '/' + name
            xml.item do
              xml.title name
              xml.description name
              xml.link item_link
              xml.guid item_link
              xml.enclosure :url => item_link
            end
          end
        end
      end
    end
  end
end